Title: Underlying Mechanisms of Cerebellar tDCS Abstract Common symptoms reported with schizophrenia and autism spectrum disorders include poor motor coordination, a deficiency also manifested in cerebellar injuries. Conversely, cerebellar injury patients often suffer from cognitive deficits, including impaired timing, attention, memory and language. Interestingly, changes in cerebellar anatomy are among the most reliable indicators of autism. Therefore, interventions targeting the cerebellum are emerging as an alternative strategy to treat cognitive disorders. Transcranial direct current stimulation (tDCS) of the cerebellum, an easy-to-apply, noninvasive, and safe intervention, has seen a surge of clinical reports in recent years suggesting that it improves motor learning, cognitive and emotional processes. However, few animal studies have investigated the electrophysiological mechanisms underlying the beneficial effects of tDCS on the cerebellar function. The primary objective of the current proposal is to generate the animal experimental data essential to identify the synaptic, cellular, and network level mechanisms by which tDCS impacts the cerebellar function. Classical trace conditioning of the eyeblink response will be used as a model cognitive task that requires coordination of the cerebellum and the prefrontal cortex. The neural mechanisms of how cerebellar tDCS modulates the trace eyeblink conditioning will be investigated in behaving animals. The fundamental knowledge gained through this investigation can be extrapolated to other cognitive and psychiatric disorders that involve the cerebellum and their treatment with tDCS.